(indices for) climate extremes ra vi clips workshop erfurt, germany, 12-18 june 2003 albert klein...
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(Indices for) Climate Extremes
RA VI CLIPS workshopErfurt, Germany, 12-18 June 2003
Albert Klein TankKNMI, the Netherlands
Acknowledgement: ECA&D-participants
Guide
1. How to define extremes and analyse changes in extremes?
2. Indices for daily T and R extremes in ECA&D
3. Observed trends in Europe, 1946-now
4. Indices and applications / climate services
5. Hands-on training using ClimDex (NCDC/NOAA)
[thanks Volker(H), Patricia &
Stefan]
Guide
1. How to define extremes and analyse changes in extremes?
2. Indices for daily T and R extremes in ECA&D
3. Observed trends in Europe, 1946-now
4. Indices and applications / climate services
5. Hands-on training using ClimDex (NCDC/NOAA)
!
www.cred.be
WMO status of global climate in 2002
www.wmo.ch
www.dwd.de/research/gpcc/
Guide
1. How to define extremes and analyse changes in extremes?
2. Indices for daily T and R extremes in ECA&D
3. Observed trends in Europe, 1946-now
4. Indices and applications / climate services
5. Hands-on training using ClimDex (NCDC/NOAA)
Recall from yesterday: ECA&D
Initiated by ECSN/EUMETNET Co-ordinated by KNMI (Voluntary) participation of RA VI countries Report and papers issued in 2002 New start in January 2003; next report in 2006 Now is the time to join!
If you want your free copy,just send an e-mail to: kleintan@knmi.nl
Concept of ECA&D
Copies of daily data series collated at KNMI Core set of indices for extremes calculated using
fixed definitions (CCL/CLIVAR ETCCMD) Results presented at website and discussed with
participants Results are European input to worldwide analyses
(e.g. in preparation for IPCC 4AR) Results are also used by e.g. EEA
Data QC & Homogeneity
Participants perform QC on daily data submitted 4 common statistical tests applied on derived
monthly and annual series Only confident station series kept for further analyses Use of MASH for homogenisation of monthly series
explored in co-operation with HMS (Szentimrey) How to homogenize daily series is still an open
question
Temperature
Wijngaard et al., Int. J. of Climatol., 2003
www.knmi.nl/samenw/eca/
Day-count indices of extremes
www.knmi.nl/samenw/eca/
Day-count indices of extremes
www.knmi.nl/samenw/eca/
www.knmi.nl/samenw/eca/
Relation between relative trend bq/X required for 80% detection probability (5% level) and series length Nfor extreme events with average return period Tret
Klein Tank and Können, J. Climate (accepted)
21365~ retTXbq
6x
23~ NXbq
3x
Day-count indices of extremes
IPCC-TAR, Ch.2, Folland and Karl
upper 10-ptile 1961-1990
the year 1996
lower 10-ptile1961-1990
upper 10-ptile 1961-1990
the year 1996
lower 10-ptile1961-1990
“cold nights”
upper 10-ptile 1961-1990
the year 1996
lower 10-ptile1961-1990
“cold nights”
“warm nights”
www.knmi.nl/samenw/eca/
www.knmi.nl/samenw/eca/
www.knmi.nl/samenw/eca/
Easterling et al. (BAMS, 2000) in IPCC-TAR
Linear trends in rainy season, last ~50 years
“Amplified” response of very wet days
Precipitation fraction due to very wet days “R95%tot”
1) Identify very wet days using a site specific threshold = 95th percentile at wet days in the 1961-90 period
2) Determine fraction of total precipitation in each year that is due to these days
3) Trend analysis in series of fractions
www.knmi.nl/samenw/eca/
www.knmi.nl/samenw/eca/
www.knmi.nl/samenw/eca/
Guide
1. How to define extremes and analyse changes in extremes?
2. Indices for daily T and R extremes in ECA&D
3. Observed trends in Europe, 1946-now
4. Indices and applications / climate services
5. Hands-on training using ClimDex (NCDC/NOAA)
European temperature trends
Recent trends (1946-1999) in temperature extremes reflect the general warming: fewer cold extremes, more warm extremes
Averaged over all stations, the first decades of slight cooling saw narrowing of temperature distributions, whereas the last decades of strong warming saw widening of temperature distributions
IPCC-TAR: “lengthening of the freeze-free season in most
mid- and high latitude regions” “reduction in frequency of extreme low monthly
and seasonal average temperatures and smaller increase in frequency of extreme high average temperatures”
European precipitation trends
Averaged over Europe, all indices of wet extremes saw increases between 1946-1999, although spatial trend coherence is low and many station trends are not significant
The index that represents the fraction of the annual amount due to very wet days gives a signal of disproportionate large changes in the extremes
IPCC-TAR: “2 to 4% increase in frequency of heavy events in
mid- and high latitudes of the NH” “in regions where total precipitation has
increased ... even more pronounced increases in heavy precipitation events”
www.knmi.nl/samenw/eca/
Frich et al. (Clim. Res., 2002) in IPCC-TAR
APN 2002 (Della-Marta, Haylock et al.) www.bom.gov.au/bmrc/csr/apn/
Trends 1961-2001
Caribbean workshop, Jamaica 2001 (Peterson et al., 2002, JGR)
Trends in 5-day rainfall total 1961-1990
Africa workshop, Casablanca 2001
WMO/CCL
1. OPAG2: Monitor. and Anal. of Clim. Var. and Change
2.3 ETCCDMI; indices of daily to seasonal extremes in
observations and models
2. OPAG3: CLIPS
3.8 ET on Health-related climate indices and their use in early
warning systems (Jendritzky)
3.10 Rapporteur(s) on use of climate indices in various
application areas (Akentyeva/Khlebnikova)
Guide
1. How to define extremes and analyse changes in extremes?
2. Indices for daily T and R extremes in ECA&D
3. Observed trends in Europe, 1946-now
4. Indices and applications / climate services
5. Hands-on training using ClimDex (NCDC/NOAA)
Indices and applications/climate services
Indices give no answer to the question of the ‘return period’ concept under climate change conditions
Core set of indices designed for research (CCD), but clear impact relevance:
Physical limits like in “Fd” index: no. of frost days Growing season length, heating degree days, no.
of consecutive dry days Percentile thresholds -> local infrastructure is
designed to withstand local climate Indices for more common events can be regarded as
indicative for more extreme events causing disasters
Some final comments
ECA&D needs to include few ‘missing’ countries and consider more elements
ECA&D has to address the cause of observed changes/trends in subregions/countries, e.g. by studying the relation with variability in atmospheric circulation (NAO)
Need to consider more advanced analysis to supplement the ‘simple’ descriptive indices
For climate services:need to consider multi-element/complex indices and user/application-specific indices
Guide
1. How to define extremes and analyse changes in extremes?
2. Indices for daily T and R extremes in ECA&D
3. Observed trends in Europe, 1946-now
4. Indices and applications / climate services
5. Hands-on training using ClimDex (NCDC/NOAA)
Hands-on training ClimDex
Need for standardized procedures and software ECA&D website lists internationally agreed definitions
of a basic set of core indices for extremes ClimDex software for calculating subset of core
indices written by Gleason/Peterson (NCDC/NOAA) ClimDex was used in WMO sponsored APN, Carribean
& African workshops on extremes Still recognize the need for more complete guide on
indices and software
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